Cards are a common organizing unit for modern user interfaces (UI). At their core, they’re just rectangular containers with borders and padding. However, when utilized properly to group related information, they help users better digest, engage, and navigate through content. This is why most successful dashboard/UI frameworks make cards a core feature of their component library. This article provides an overview of the API that bslib provides to create Bootstrap cards.
Setup code
To demonstrate that bslib cards work outside of Shiny (i.e., in R Markdown, static HTML, etc), we’ll make repeated use of statically rendered htmlwidgets like plotly and leaflet. Here’s some code to create those widgets:
library(bslib)
library(shiny)
library(htmltools)
library(plotly)
library(leaflet)
plotly_widget <- plot_ly(x = diamonds$cut) %>%
config(displayModeBar = FALSE) %>%
layout(margin = list(t = 0, b = 0, l = 0, r = 0))
leaflet_widget <- leafletOptions(attributionControl = FALSE) %>%
leaflet(options = .) %>%
addTiles()Shiny usage
Cards work equally well in Shiny. In the
examples below, replace plotly_widget with
plotlyOutput() and leaflet_widget with
leafletOutput() to adapt them for Shiny server-rendered
plots/maps.
Hello card()
A card() is designed to handle any number of “known”
card items (e.g., card_header(), card_body(),
etc) as unnamed arguments (i.e., children). As we’ll see shortly,
card() also has some useful named arguments (e.g.,
full_screen, height, etc).
At their core, card() and card items are just an HTML
div() with a special Bootstrap class, so you can use
Bootstrap’s utility classes to customize things like colors,
text, borders,
etc.
card(
card_header(
class = "bg-dark",
"A header"
),
card_body(
markdown("Some text with a [link](https://github.com)")
)
)Some text with a link
Implicit card_body()
If you find yourself using card_body() without changing
any of its defaults, consider dropping it altogether since any direct
children of card() that aren’t “known” card()
items, are wrapped together into an implicit card_body()
call.1
For example, the code to the right generates HTML that is identical to
the previous example:
card(
card_header(
class = "bg-dark",
"A header"
),
markdown("Some text with a [link](https://github.com).")
)Some text with a link.
Restricting growth
By default, a card()’s size grows to accommodate the
size of it’s contents. Thus, if a card_body() contains a
large amount of text, tables, etc., you may want to specify a
height or max_height. That said, when laying
out multiple cards, it’s likely best not
to specify height on the card(), and instead, let the
layout determine the height layout_column_wrap().
Although scrolling is convenient for reducing the amount of space
required to park lots of content, it can also be a nuisance to the user.
To help reduce the need for scrolling, consider pairing scrolling with
full_screen = TRUE (which adds an icon to expand the card’s
size to the browser window). Notice how, when the card is expanded to
full-screen, max_height/height won’t effect
the full-screen size of the card.
card(
max_height = 250,
full_screen = TRUE,
card_header(
"A long, scrolling, description"
),
lorem::ipsum(paragraphs = 3, sentences = 5)
)Sit ultrices lacus dictum, tristique cum metus, gravida gravida nibh tristique cursus gravida. Faucibus condimentum odio maecenas pulvinar at rutrum potenti. In vel porttitor vehicula porttitor eu sed mus. Sem nunc suspendisse ac per natoque, dictumst nulla convallis phasellus. Hac rutrum tristique a id; enim justo enim.
Amet tristique dictumst, mi magna, donec facilisis porta? Erat massa auctor netus vel diam, donec netus turpis facilisis mus nisi mollis. Aliquet dictumst ultricies senectus torquent mauris mollis, neque cras faucibus id urna dapibus. Ad ad per sem interdum lacus fusce lacus torquent platea ut? Lacus aptent fringilla tempus mus potenti duis ligula – ornare enim tortor metus!
Sit euismod orci est pretium laoreet conubia eget eget ullamcorper iaculis? Sodales feugiat varius nullam, mauris natoque metus odio, habitasse curae nostra! Cum ut auctor sodales, nostra nostra? Tristique volutpat vitae aliquet gravida aenean aliquet semper per ornare volutpat tortor scelerisque! Odio mus per diam feugiat quam integer semper nullam laoreet?
Filling outputs
A card()’s default behavior is optimized for
facilitating filling layouts. More
specifically, if a fill item (e.g.,
plotly_widget), appears as a direct child of a
card_body(), it resizes to fit the card()s
specified height. This means, by specifying height = 250
we’ve effectively shrunk the plot’s height from its default of 400 down
to about 200 pixels. And, when expanded to full_screen, the
plot grows to match the card()’s new size.
card(
height = 250,
full_screen = TRUE,
card_header("A filling plot"),
card_body(plotly_widget)
)Most htmlwidgets (e.g., plotly, leaflet, etc) and some other Shiny
output bindings (e.g, plotOutput(),
imageOutput(), etc) are fill items by
default, so this behavior “just works” in those scenarios. And, in some
of these situations, it’s helpful to remove card_body()’s
padding, which can be done via spacing
& alignment utility classes.
card(
height = 275,
full_screen = TRUE,
card_header("A filling map"),
card_body(
class = "p-0",
leaflet_widget
),
card_footer(
class = "fs-6",
"Copyright 2023 RStudio, PBC"
)
)Fill item(s) aren’t limited in how much they grow
and shrink, which can be problematic when a card becomes very small. To
work around this, consider adding a min_height on the
card_body() container. For example, try using the handle on
the lower-right portion of this card example to make the card
taller/smaller.
This interactive example is a bit contrived in that we’re using CSS
resize to demonstrate how to make plots that don’t shrink beyond a
certain point, but this concept becomes quite useful when implementing
page-level filling layouts (i.e.,
page_fillable()) with multiple
cards.
card(
height = 300,
style = "resize:vertical;",
card_header("Plots that grow but don't shrink"),
card_body(
min_height = 250,
plotly_widget,
plotly_widget
)
)Troubleshooting fill
As you’ll learn more about in filling
layouts, a fill item loses its ability to fill when
wrapped in additional UI element that isn’t a fillable
container. To fix the situation, use as_fill_carrier() to
allow the additional element to carry the potential to fill from the
card_body() down to the fill item.
Multiple card_body()
A card() can have multiple card_body()s,
which is especially useful for:
- Combining both resizable and non-resizable contents (i.e., fill items and non-fill).
- Allowing each
card_body()to have their own styling (via inline styles and/or utility classes) and resizing limits (e.g.,min_height).
For example, when pairing filling output with scrolling content, you
may want min_height on the filling output since the
scrolling content will force it to shrink:
card(
height = 375,
full_screen = TRUE,
card_header(
"Filling plot, scrolling description"
),
card_body(
min_height = 200,
plotly_widget
),
card_body(
class = "lead container",
lorem::ipsum(paragraphs = 10, sentences = 5)
)
)Ipsum viverra dictumst rutrum augue sem. Commodo dapibus auctor semper congue mattis inceptos fames fringilla feugiat porttitor risus scelerisque. Vestibulum euismod proin pretium netus suscipit penatibus, posuere non mi faucibus tempus! Sociosqu rutrum tempor, mauris leo fringilla commodo! Parturient ullamcorper nulla leo fames varius non?
Consectetur fames aptent pulvinar condimentum tempus pulvinar dictum posuere. Primis varius sem sociosqu luctus elementum non sodales, fermentum tempus. Non netus sociosqu nec – faucibus hac lacinia etiam pretium praesent? Hendrerit in sed litora tincidunt id porta praesent. Na praesent.
Sit aliquam condimentum faucibus placerat? Himenaeos convallis ligula mattis nam dis vulputate suspendisse risus tristique interdum tellus fames! Sagittis turpis purus erat sollicitudin, turpis augue, interdum blandit mauris facilisis. Semper tristique sem curae cursus, neque class fames feugiat. Imperdiet mollis vehicula ullamcorper, aptent pellentesque, rutrum leo porttitor ut fusce vehicula per?
Adipiscing taciti turpis aptent sociosqu vehicula, dapibus vel potenti. Fermentum laoreet, aptent dis purus tristique, netus, justo donec luctus. Convallis nascetur integer; parturient mauris felis faucibus sollicitudin! Penatibus euismod, dapibus in; platea vehicula magna ante posuere! Platea aliquet varius tempus mattis urna posuere rhoncus montes est eleifend molestie nunc curae, fermentum molestie nam et hendrerit?
Consectetur class quisque tristique lobortis, a, himenaeos primis odio porttitor! Nisl pellentesque curabitur orci tristique bibendum curabitur non massa euismod. Nisl taciti fames sociis dis tempus, eros dapibus consequat – erat himenaeos primis. Montes eget per, accumsan imperdiet; curabitur ad est ac. Tellus sociosqu habitant.
Consectetur fusce etiam pulvinar, nec neque etiam penatibus suscipit scelerisque aenean. Laoreet non luctus, libero etiam fames primis? Dui dictum aptent fermentum habitant dignissim himenaeos parturient facilisis. Per ullamcorper quisque tempor integer aliquet elementum platea bibendum sociis! Cursus convallis sagittis egestas integer lectus aptent nam, lobortis pulvinar elementum facilisi porta lobortis tellus magna in fringilla.
Adipiscing sodales hendrerit et convallis id, nam lobortis interdum penatibus eleifend cras! Elementum eget purus euismod odio eget mauris posuere vel natoque vivamus cubilia. Dictumst dignissim, volutpat nulla porta viverra purus, at habitasse! Magna phasellus vestibulum purus erat habitasse? Erat luctus lacus porttitor et ridiculus quisque – tempus a fusce ante.
Elit libero hac arcu varius massa purus platea id suscipit nostra cubilia. Cubilia felis cum, aptent fusce luctus, nulla placerat odio quis nostra, porttitor tortor aliquet. Sociosqu mus vehicula facilisi interdum eleifend nec ullamcorper curae. Etiam pellentesque malesuada risus eros turpis tristique facilisis enim. Facilisi mus varius neque consequat potenti cras!
Consectetur pellentesque duis fames massa dui aptent himenaeos mauris convallis aliquet imperdiet. Ridiculus ac proin vel etiam gravida arcu, lobortis class litora? Quam conubia sem lacinia semper pretium, facilisis class nostra tincidunt. Etiam imperdiet vehicula mus facilisi egestas bibendum. Mi fringilla justo libero dignissim ad dignissim mi, blandit imperdiet hac sed?
Adipiscing nostra purus odio mauris aliquam interdum semper mi ut mattis egestas. Morbi faucibus erat sociosqu diam, commodo risus dis leo nascetur. Habitasse dictum feugiat pulvinar accumsan, venenatis erat turpis commodo massa? Felis mi sociosqu rhoncus, enim, praesent dui ante rhoncus eleifend bibendum eros torquent. Interdum accumsan phasellus parturient imperdiet nibh dapibus.
Also, when the content has a fixed size, and should not be allowed to
scroll, set fill = FALSE:
card(
height = 350,
full_screen = TRUE,
card_header(
"Filling plot, short description"
),
plotly_widget,
card_body(
fill = FALSE,
card_title("A subtitle"),
p(class = "text-muted", "And a caption")
)
)A subtitle
And a caption
Multiple columns
As you’ll learn in column-based
layouts, layout_column_wrap() is great for multi-column
layouts that are responsive and accommodate for filling output. Here we have an equal-width
2-column layout using width = 1/2, but it’s also possible
to have varying column
widths.
card(
height = 350,
full_screen = TRUE,
card_header("A multi-column filling layout"),
card_body(
min_height = 200,
layout_column_wrap(
width = 1/2,
plotOutput("p1"),
plotOutput("p2")
)
),
lorem::ipsum(paragraphs = 3, sentences = 5)
)Elit malesuada cursus, molestie auctor hac morbi. Ac mauris massa magnis dis augue – tortor porta molestie vehicula himenaeos. Pellentesque ac nam rutrum quis justo diam facilisi lacinia dis accumsan, blandit nec ac in. Bibendum luctus sem leo metus, eget; molestie nunc ad. Convallis tempus habitasse in platea maecenas dis ac hac donec nec netus facilisi lobortis massa!
Amet gravida semper pellentesque inceptos facilisi – viverra non venenatis. Aliquet accumsan natoque tristique ante duis ultrices maecenas curabitur ut, himenaeos dictum? Proin interdum, volutpat, laoreet ut ultrices iaculis morbi egestas ultrices nisi erat! Sodales aenean dis penatibus parturient interdum integer, dis velit rhoncus. Luctus velit, tortor commodo purus aliquam; luctus feugiat.
Amet pharetra taciti nibh platea vulputate nullam. Aptent nullam faucibus massa montes, gravida varius himenaeos sem condimentum justo? Etiam luctus habitasse facilisis curae. Elementum vulputate bibendum luctus mollis. Nulla placerat hendrerit convallis tristique dis, eleifend per fringilla augue malesuada pellentesque netus ultrices, maecenas suscipit lacinia himenaeos; phasellus porta pellentesque netus cum.
Multiple cards
layout_column_wrap() is especially nice for laying out
multiple cards since each card in a particular row will have the same
height (by default). Learn more in column-based layouts.
layout_column_wrap(
width = 1/2,
height = 300,
card(full_screen = TRUE, card_header("A filling plot"), plotly_widget),
card(full_screen = TRUE, card_header("A filling map"), card_body(class = "p-0", leaflet_widget))
)Multiple tabs
navset_card_tab() and navset_card_pill()
make it possible to create cards with multiple tabs or pills. These
functions have the same full_screen capabilities as normal
card()s as well some other options like title
(since there is no natural place for a card_header() to be
used). Note that, each nav_panel() object is similar to a
card(). That is, if the direct children aren’t already card
items (e.g., card_title()), they get implicitly wrapped in a
card_body().
library(leaflet)
navset_card_tab(
height = 450,
full_screen = TRUE,
title = "HTML Widgets",
nav_panel(
"Plotly",
card_title("A plotly plot"),
plotly_widget
),
nav_panel(
"Leaflet",
card_title("A leaflet plot"),
leaflet_widget
),
nav_panel(
shiny::icon("circle-info"),
markdown("Learn more about [htmlwidgets](http://www.htmlwidgets.org/)")
)
)Sidebars
As you’ll learn more about in sidebar
layouts, layout_sidebar() just works when placed inside
in a card(). In this case, if you want fill
items (e.g., plotly_widget) to still fill the card
like we’ve seen before, you’ll need to
set fillable = TRUE in layout_sidebar().
card(
height = 300,
full_screen = TRUE,
card_header("A sidebar layout inside a card"),
layout_sidebar(
fillable = TRUE,
sidebar = sidebar(
actionButton("btn", "A button")
),
plotly_widget
)
)Static images
card_image() makes it easy to embed static (i.e.,
pre-generated) images into a card. Provide a URL to href to
make it clickable. In the case of multiple card_image()s,
consider laying them out in multiple cards
with layout_column_wrap() to produce a grid of clickable
thumbnails.
card(
height = 300,
full_screen = TRUE,
card_image(
file = "shiny-hex.svg",
href = "https://github.com/rstudio/shiny"
),
card_body(
fill = FALSE,
card_title("Shiny for R"),
p(
class = "fw-light text-muted",
"Brought to you by RStudio."
)
)
)
Shiny for R
Brought to you by RStudio.
Flexbox
Both card() and card_body() default to
fillable = TRUE (that is, they are CSS flexbox
containers), which works wonders for facilitating filling outputs, but it also leads to
surprising behavior with inline tags (e.g., actionButton(),
span(), strings, etc). Specifically, each inline tag is
placed on a new line, but in a “normal” layout flow
(fillable = FALSE), inline tags render inline.
card(
card_body(
fillable = TRUE,
"Here's some", tags$i("inline"), "text",
actionButton("btn1", "A button")
),
card_body(
fillable = FALSE,
"Here's some", tags$i("inline"), "text",
actionButton("btn2", "A button")
)
)That said, sometimes working in a flexbox layout is quite useful,
even when working with inline tags. Here we leverage flexbox’s gap
property to control the spacing between a plot, a (full-width) button,
and paragraph. Note that, by using markdown() for the
paragraph, it wraps the results in a <p> tag, which
means the contents of the paragraph are not longer subject to
flexbox layout. If we wanted, we could do something similar to render
the actionButton() inline by wrapping it in a
div().
card(
height = 325, full_screen = TRUE,
card_header("A plot with an action links"),
card_body(
class = "gap-2 container",
plotly_widget,
actionButton(
"go_btn", "Action button",
class = "btn-primary rounded-0"
),
markdown("Here's a _simple_ [hyperlink](https://www.google.com/).")
)
)Here's a simple hyperlink.
In addition to gap, flexbox has really nice ways of handling otherwise difficult spacing and alignment issues. And, thanks to Bootstrap’s flex utility classes, we can easily opt-in and customize defaults.
card(
height = 300, full_screen = TRUE,
card_header(
class = "d-flex justify-content-between",
"Centered plot",
checkboxInput("check", " Check me", TRUE)
),
card_body(
class = "align-items-center",
plotOutput("id", width = "75%")
)
)Shiny
Since this article is statically rendered, the examples here use
statically rendered content/widgets, but the same card()
functionality works for dynamically rendered content via Shiny (e.g.,
plotOutput(), plotlyOutput(), etc).
An additional benefit that comes with using shiny is the ability to
use getCurrentOutputInfo() to render new/different content
when the output container becomes large enough, which is particularly
useful with card(full_screen = T, ...). For example, you
may want additional captions/labels when a plot is large, additional
controls on a table, etc (see the value
boxes article for a clever use of this).
# UI logic
ui <- page_fluid(
card(
max_height = 200,
full_screen = TRUE,
card_header("A dynamically rendered plot"),
plotOutput("plot_id")
)
)
# Server logic
server <- function(input, output, session) {
output$plot_id <- renderPlot({
info <- getCurrentOutputInfo()
if (info$height() > 600) {
# code for "large" plot
} else {
# code for "small" plot
}
})
}
shinyApp(ui, server)Appendix
The following CSS is used to give plotOutput() a
background color; it’s necessary here because this documentation page is
not actually hooked up to a Shiny app, so we can’t show a real plot.